1. Field of the Invention
The invention relates to a method of emitting sound signals from a memory card or a smart card.
2. Discussion of the Background
It is now common practice to use a memory card or a smart card as a key for giving access to a service or as means for transferring data. When this access or transfer is performed remotely, it is also known to use so-called xe2x80x9cvoicexe2x80x9d cards where data is transmitted over a telephone line by acoustic coupling with a telephone.
A voice card is described in particular in document EP-A-0 664 633 where data is converted into sound signals by means of a piezoelectric transducer housed in the card, and those signals are emitted in voice form by the transducer and are transmitted to the telephone line via the microphone of the telephone. Emitting signals in xe2x80x9cvoice formxe2x80x9d means emitting at any frequency lying in the passband of the telephone network.
Specifically, the user holds the telephone handset in one hand and the card in the other hand and brings the card up to the microphone of the handset, after which the user presses a key present on the card to activate the process of transmitting in voice form data that is recorded in the card.
Transmitting data in that way is not without its problems, in particular concerning manufacture of the card. The piezoelectric transducer must be received in a cavity that provides sufficient space to define an acoustic chamber. In spite of the small thickness of the card, 0.76 mm according to ISO standards, the dimensions of the cavity must nevertheless be sufficient to obtain good performance from the acoustic point of view, but that gives rise to a card that is fragile from the mechanical point of view. It is therefore necessary to find a compromise which becomes increasingly difficult to achieve with reducing card thickness. In addition, the acoustic chamber of the piezoelectric transducer must communicate with the outside via holes formed in the card. This means that the card is sensitive to constraints of the external environment, and in particular to moisture which can cause the piezoelectric transducer to misfunction.
Starting from in-depth examination of this state of the art, and seeking to mitigate specifically the problems posed by manufacture while complying with the thickness constraint imposed for this type of card, the Applicant has been led to design a new way of emitting sound which constitutes the subject matter of the present application.
To this end, the invention provides a method of emitting sound signals from a memory card or a smart card, the method being characterized in that it consists in using the card as a vibrating membrane, and in setting the card into vibration by means of an excitation device housed in the card for transforming it into a source that emits sound signals.
According to another characteristic of the invention, the method consists in using an excitation device which produces mechanical vibration, and in housing the source inside the card in such a manner as to secure it thereto so that the mechanical vibration produced by the excitation device is transmitted directly to the card to cause it to vibrate and cause it to emit sound signals.
Such a method of emitting sound signals presents the particular advantage of facilitating the operations of manufacturing the card. It is no longer necessary to provide an acoustic chamber in the cavity which receives the excitation device. This simplifies manufacture and also improves performance both acoustically and mechanically.
Thus, and in spite of appearing paradoxical, the small thickness which is a constraint in manufacturing a voice card of the prior art becomes an advantage in manufacturing a card that implements the method of the invention. In other words, the thinner the card, the better the performance of the method of the invention.
In addition, since the card is no longer pierced by holes which used to be necessary for passing the sound wave, the emission method of the invention can advantageously be implemented in a card which is waterproof.
In general, a voice card is activated using a mechanical key integrated in the card.
According to another characteristic of the invention, the emission method is activated from a touch-sensitive key, thereby making it easier to integrate such a key in a card of small thickness.
The invention also proposes a memory card or a smart card for implementing the emission method of the invention, the card incorporating at least one controlling electronic micromodule comprising in particular processor circuits and a memory in which binary data is stored, an excitation device connected to the micromodule to convert the binary data into sound signals, a vibrating membrane connected to the excitation device to emit said sound signals, and an actuation key, the card being characterized in that the vibrating membrane is constituted by the card itself.
By way of example, the excitation device of the membrane-forming card is a device which produces mechanical vibration, such as a ceramic type piezoelectric element, and which is secured to the card by being embedded therein, for example. In which case, the piezoelectric element and the card form an electro-acoustic transducer, the piezoelectric element being excited by electrical signals delivered on the basis of binary data recorded in the card, for example.
Preferably, the excitation device of the membrane-forming card is placed in a corner of the card while enabling the card to vibrate substantially over its entire area.
This position presents the particular advantage of displacing the excitation device away from the main twisting and bending axes of the card, thus also enabling the card to satisfy ISO standards concerning the mechanical stresses which the card must be capable of withstanding.
A card of the invention can be manufactured using conventional rolling or injection techniques, for example. To activate such a card, the user holds it between the fingers and activates the emission process by means of a key of the card, as with a conventional voice card. However, it is important to observe that the mere fact of the user holding the card between the fingers serves to amplify the vibration mode of the card.
According to another characteristic of the card of the invention, the activation key is constituted by a touch-sensitive key which, compared with a mechanical key, presents the advantage of having no moving parts.
Like the card of the document cited in the introduction, such a card can be used in particular for the purpose of emitting binary data in voice form for transmission over a telephone line by acoustic coupling with a telephone. Under such circumstances, the card of the invention has the advantage of not requiring accurate positioning relative to the microphone of the telephone.